Timing devices which depend on the flow of a material through an orifice of a selected size are, of course, well-known. The commonest example is the hour-glass in which the material which flows through the orifice is a fine powder. However, as is obvious, similar devices dependent upon the flow of liquid through an orifice also can be used as timing devices. Also, the flow of liquid through an orifice has been used for other purposes, two such purposes being determination of the flow rate of the liquid and determination of the viscosity of the liquid. Peculiarly, both of these latter measurements depend upon orifices. This fact is surprising because measurement of the flow rate by the use of an orifice depends upon the fact that flow through a square-edged orifice is independent of viscosity, whereas determination of viscosity depends upon flow rate through an orifice in the form of a capillary. The contrast between these two types of measurements makes it clear that viscosity can give rise to problems in trying to measure the flow rate of a liquid where the orifice is other than square-edged. This problem has received considerable attention in the development of the variable-orifice flow meters which were originally known as rotameters, such meters being based upon the use of a plummet suspended by flowing liquid in a tube of gradual taper. The problem has been solved by the use of plummets of special configuration which, in effect, provide a variable orifice which has similarity to the square-edged orifice. Since such plummets are relatively expensive, attempts were made to use a spherical ball as the plummet. However, the spherical ball or float gives results which are sensitive to the viscosity of the liquid flowing through the meter. Then, since the viscosity of a liquid is strongly sensitive to temperature, the flow rate measurement provided by such a meter is likewise sensitive to temperature. Accordingly, it would appear that it would be difficult to provide a timer in which the transit time of a float through a flotation liquid is essentially independent of temperature, even taking into account the fact that liquids having a relatively low viscosity index (the rate of change of viscosity with temperature) are now available. Nevertheless, it would be desirable to be able to provide such a timer, especially without the necessity for the use of a plummet or float of complex profile.